According to CNN, the bombers entered the Alaskan Air Defence Identification Zone some 700 nautical miles southwest of Anchorage.

The U.S. military has spotted Russian military aircraft flying off the coast of Alaska for the fourth time in as many days, a U.S. defense official has said. The Russian planes remained in global air space the entire time.

U.S. fighter jets intercepted two Russian bombers in worldwide airspace 100 miles from Kodiak Island, Alaska on Monday.

While military officials don't seem too concerned about the Russian fly bys, the mysterious missions raise questions because the Russians haven't flown this close to Alaska in two years. A US defense official told the news site that this was "nothing out of the ordinary".

Two F-22 Raptor stealth jets and an E-3 Sentry early warning plane were dispatched in global airspace on Monday night. The Kremlin and Tillerson both said that relations had eroded to the lowest point under Trump's presidency after the secretary's visit. There is "no other way to interpret this other than as strategic messaging", an official told CNN.

But one U.S. defence expert says the missions are part of Russian President Vladimir Putin trying "to prove Russia is back in the game". The flights mark the first time since 2015 that Russian planes have approached the USA mainland. Indeed that's the only conclusion that can be drawn while recalling that the most recent time this happened was in 2015 when Russian bombers flirted 40 miles off the Californian coast.